When its controller has three or more Instants or Sorceries in the graveyard, it flips into the Voracious Reader, which has the Prowess mechanic and also makes Instants and Sorceries cast by its controller cost one less generic mana
Value, value, value for pretty much any green deck, this green creature is one of those cards getting people to (incorrectly) call the set Commander Horizons
Still, it cant sac after blockers, which is a big drawback, and is still 4 mana
For example, if you have with no restrictions on it and that can be used only to cast artifact spells, you'll end up with , that can be used only to cast artifact spells, and that can be used for anything.
[127] It was released in Japan in December 1998 [128] and later in North American and Europe in 2000, [129] reappearing in the Nintendo 3DS Virtual Console released in 2014